The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Centrifugal casting refers to a method forming casting by using centrifugal force generated when rotating a mold at a high speed during injecting and then coagulating molten metal. In order to cast via the centrifugal casting method, it needs to inject the molten metal into the mold rapidly and uniformly so that the molten metal can be coagulated from the surface contacted with the mold toward the inside thereof, whereby high-quality casting products without internal defects can be obtained. For this, the rotating speed of the mold, the injecting temperature and the injecting speed of the molten metal should be uniformly maintained. Further, if the mold is not sufficiently preheated, the molten metal is immediately coagulated the moment it is injected into the mold such that air bubbles inside the molten metal are coagulated with collected state, thereby causing internal quality problems.
In the case of continuously casting the high-temperature (660˜750°) molten metal such as aluminum, since the temperature of the mold rises consistently, the coagulation is delayed or local heat isolation is generated depending on the products shapes, and therefore there has been the problem that casting defects (air bubble defect, contraction defect) are generated inside the casting products. In order to solve this problem, the mold should be cooled during the casting process. However, since the mold rotates at 300˜3,000 rpm for the centrifugal casting, it is difficult to apply the circulation type cooling apparatus using cooling water.
The conventional mold cooling method not using the cooling water has used the processes of cooling the mold by insufflating cool air into the inside of the mold or by injecting cool air to the surface of the mold in a state of stopping casting works. However, there have been the problems that the casting process should be stopped in order to cool the inside of the mold and the method cooling the surface of the mold has the low cooling efficiency.
The conventional mold cooling method using cooling water is concretely well-known as “A blank casting apparatus for stainless steel pipe flange (Korean Patent Publication No. 10-2002-0037429 (May 21, 2002)).
Technology exists that cools a mold by supplying cooling water to cooling jacket formed at the lower surface wall of the rotating mold for casting a pipe. This circulation type cooling system, in which a cooling water inflow pipe and a cooling water outflow pipe are installed inside a hollow shaft, is applied such that the cooling water is supplied to the cooling jacket through the hollow shaft and then discharged through the hollow shaft again. If the rotating mold rotates, the phenomenon that cooling water is heeled over toward the outer circumference surface direction of the cooling jacket by centrifugal force occurs. As described above, if the cooling water is congested outside, there has been the problem that the cooling water is heated such that the cooling efficiency of the mold is reduced and the cooling water flowed through the cooling water inflow pipe is directly flowed out through the cooling water outflow pipe.
Because of these problems, it may be possible to change the shape of the cooling jacket from a chamber shape to a pipe shape. Even in this case, however, the problem that the cooling water is isolated and congested at a variation portion formed at the pipe has been generated. In order to solve this, a high pressure pump more than 300 bar for further increasing the cooling water supply pressure has been required.